The overall goal of this study is to obtain a more complete understanding of the role that physiologic changes induced by stress play in the development of ethnic differences in essential hypertension. The physiologic response to stress is a dynamic process. It includes the response to the stressor per se AND the physiologic response, which bring the body into homeostasis. The vast majority of research has focused on the physiologic response during stress while homeostatic changes following stress have largely been ignored. There is very little information about group differences. The general hypothesis of this proposal is as follows: African-Americans compared to Caucasians show slower natriuresis during and following the stress coupled with greater vasoconstriction. This will result in an extended period of elevated blood pressure following stress, exposing these individuals to an increased BP load, which leads to the premature development of end organ changes. Therefore, the aims of this study are: 1) contrast hemodynamic regulation in African-American and Caucasian subjects before, during, and two hours following a 60 minute stress period; 2) contrast hormonal regulation in African-American and Caucasian subjects during the procedure; 3) contrast levels of Na+ handling between African-American and Caucasian subjects during the procedure; 4) determine the relationship between measures of target organ change and BP changes during the recovery period. The proposed study will add considerably to the minimal knowledge of the factors underlying, and significance of, an impaired homeostatic process by a) for the first time identifying hormonal mechanism associated with the response; and b) for the first time determining the clinical significance of the response by relating it to target organ changes.